A quick-reference chart for how much water to drink based on your body weight, in both kilograms and pounds, using the 30–35 mL per kg dietetic estimation formula — plus how to adjust it for exercise, climate and pregnancy.
A commonly used clinical and dietetic estimation range is roughly 30–35 millilitres of fluid per kilogram of body weight per day. In pounds, that works out to roughly 0.5 fl oz per pound at the low end. This is a fluids-only estimate — separate from "total water" reference values like NASEM's 3.7 L/2.7 L figures, which also include water from food.
Enter your exact weight, activity level and climate to get a full personalised estimate in litres, mL, fl oz and cups.
Open the Water Intake Calculator →Find your approximate body weight below to see the estimated daily fluid range. These figures assume a sedentary-to-lightly-active adult in a temperate climate — see the adjustment section below for exercise and heat.
| Weight (kg) | Weight (lb) | 30 mL/kg | 35 mL/kg |
|---|---|---|---|
| 45 kg | 99 lb | 1.35 L | 1.58 L |
| 50 kg | 110 lb | 1.50 L | 1.75 L |
| 55 kg | 121 lb | 1.65 L | 1.93 L |
| 60 kg | 132 lb | 1.80 L | 2.10 L |
| 65 kg | 143 lb | 1.95 L | 2.28 L |
| 70 kg | 154 lb | 2.10 L | 2.45 L |
| 75 kg | 165 lb | 2.25 L | 2.63 L |
| 80 kg | 176 lb | 2.40 L | 2.80 L |
| 85 kg | 187 lb | 2.55 L | 2.98 L |
| 90 kg | 198 lb | 2.70 L | 3.15 L |
| 95 kg | 209 lb | 2.85 L | 3.33 L |
| 100 kg | 220 lb | 3.00 L | 3.50 L |
| 110 kg | 243 lb | 3.30 L | 3.85 L |
| 120 kg | 265 lb | 3.60 L | 4.20 L |
Figures rounded to two decimal places. For a weight between rows, interpolate roughly, or use the water intake calculator for an exact figure at any weight.
Body weight is one of the few inputs with a genuinely defensible, near-linear relationship to fluid needs. Larger bodies have more total tissue — including blood volume and lean mass — that needs to stay hydrated, and typically a higher resting metabolic rate, which increases water lost through breathing and normal bodily processes. This is why weight-based formulas scale up fairly consistently as body size increases, unlike some other proposed adjustments that lack solid evidence.
That said, weight is a proxy for body size, not a perfect predictor. Two people of the same weight but very different body composition — for example, differing muscle mass — will have somewhat different actual needs, since muscle holds more water than fat tissue relative to its mass. The chart above is a reasonable starting estimate, not an exact figure.
The chart above reflects a baseline, low-activity scenario. Several genuine factors will increase your actual needs above these numbers:
The full calculator combines your weight with activity level and climate for a more complete estimate than the chart alone.
Calculate My Personalised Water Intake →Weight-based formulas like 30–35 mL/kg are a genuinely useful estimation tool used in dietetics, but they have real limits. They don't account for kidney function, certain medications (particularly diuretics or fluid-restricting drugs), heart or liver conditions affecting fluid balance, or unusually high fluid losses from illness. If you have a medical condition that affects fluid balance, ask your doctor or a dietitian for individualised guidance rather than relying on a general formula.
How much water should a 150 lb person drink?
Using the 30–35 mL per kg estimation range, a 150 lb (68 kg) person needs roughly 2.0–2.4 litres of fluids a day as a baseline, before adjusting for exercise, climate or pregnancy/breastfeeding.
Is the water-per-pound-of-body-weight rule accurate?
It's a reasonable estimation range used in clinical and dietetic practice, not an official general-population recommendation or a precise individual prescription. It gives a fluids-only estimate and doesn't account for activity, climate, or medical conditions, so treat it as a starting point rather than an exact target.
Do I need more water if I weigh more?
Generally yes. Larger bodies have more tissue to hydrate and typically a higher metabolic rate, both of which increase baseline fluid needs, which is why weight-based formulas scale intake with body size.
A simple weight-based estimate — 30 to 35 mL of fluid per kilogram of body weight per day — gives a reasonable starting figure for most healthy adults, before accounting for exercise, climate, and pregnancy or breastfeeding. For a complete personalised estimate that factors in all of these, use the full water intake calculator above.